Role of pyrite on oxidative degradation of some chlorophenolic compounds with zero-valent iron/H2O2 system

The effect of a naturally occurring soil mineral, pyrite, on the degradation of 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) by Fenton process with micro scale zero-valent iron (ZVI) as the catalyst was studied in batch reactors. Our batch data show that while the CP degradation with ZVI/H₂O₂ system was adversely affected by the aggregation of ZVP particles, the use of pyrite in systems containing ZVI/H₂O₂ greatly improved the oxidative degradation of CPs. Surface measurements, including salt titration, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS), revealed that the ZVI particles and surface oxidation precipitates dispersed on pyrite particles, thus preventing ZVI particle aggregation, and subsequently promoting iron redox cycling for enhanced ZVI corrosion and surface site regeneration. Following Fenton degradation, the oxidative degradation intermediate species of CPs became significantly more biodegradable relative to their mother compounds. Overall, combining ZVI and pyrite at the optimum dose might be a cost-effective technology for developing novel treatment methods for the treatment of groundwater and wastewater contaminated with chlorophenolic chemicals.